Development of a pelagic biogeochemical model with enhanced computational performance by optimizing ecological complexity and spatial resolution

Abstract

Introducing ESTAS-AQUABC, a new software tool designed for modelling nutrient cycles and eutrophication in highly-eutrophic estuaries. Our focus on replicating intense cyanobacteria blooms and N2-fixation sets us apart from other estuary models. We account for N2-fixation by cyanobacteria, the inorganic carbon cycle, non-conservative alkalinity, and pH calculations through CO2SYS integration. AQUABC also includes ammonia-stripping at high pH in its kinetic sub-model. ESTAS-AQUABC uses box modelling approach where the fluxes between boxes are calculated by a hydrodynamical model, in our case the SHYFEM model. This approach is robust, especially when field data for calibration is scarce, saving computational time. While our model accurately reproduced pelagic N2-fixation rates, inorganic nutrient dynamics were less precise, mainly due to the absence of bentho-pelagic exchange processes. ESTAS-AQUABC provides a useful tool to investigate nutrient retention from land to open sea, which could be important to mitigate eutrophication in estuarine systems and the adjacent coastal areas.